Background: Due to the special anatomy morphology and physiological function of the mandible, it has always become a challenge to accurately reconstruct the mandibular defect in maxillofacial surgery. Digital three dimensions (3D) printing surgical guide, as the effective method for individual and accurate surgery, is a hotspot of clinical research at present. In this study, 3D printing PLA surgical guide plate was applied to reconstruct the mandibular defect with fibula flap, its clinical effect and accuracy were evaluated, which aimed to improve the accurate reconstruction of mandibular defects. Methods: After sterilization, the dimension deformation of the PLA standard specimen were measured. Eighteen patients diagnose with mandibular tumor were collected as observation objects. Then partial mandible resection and simultaneous mandible reconstruction with fibula graft were implemented according to the computer-aided design plan. The clinical effects of 3D printing PLA guide plates application were evaluated by facial contours, occlusal stability and chewing function. Through registering the postoperative computed images reconstruction with preoperative designed shape, the reconstruction accuracy was evaluated by detecting the maximum difference including the distance between lateral convex point of the condyles, the distance between medial convex point of the condyles and the horizontal contained angle between long axis of the condyles. Results: After high temperature steam sterilization, the curvature of the PLA specimen with 100% filling rate and 4.8 mm thickness were the smallest and their dimension deformation had no statistical significance (P>0.05). The minimally deformed 3D printing PLA guide plate were smoothly placed in the right place during the operation. After surgery, the face was symmetrical, the occlusal relationship was restored well and no deviation of the mandibular movement were found. The spiral computed tomography (SCT) scanning showed that the distance between lateral/medial convex points of the condyle and the horizontal contained angle were 128.34±8.68 mm, 88.69±6.75 mm and 145.87°±12.01°. Compared with preoperative design, the maximum deviation of the actual postoperative registration was 1.67±0.63, and the difference was not statistically significant (P>0.05). Conclusions: The application of 3D printing PLA guide plate in the segmental section and reconstruction of the mandible can effectively simplify the operation, and better reconstruct the continuity of the mandible. The surgical accuracy can fully meet clinical needs with relatively low prices.

A Si₃N₄ slot waveguide has the ability to confine light tightly in the slot, shows weak absorption of 980 nm pump light, and has lower transmission loss compared to a Si slot. Hence, the optical waveguide amplifier based on Er³⁺ and Yb³⁺codoped was proposed to be integrated with a Si₃N₄ slot to increase the gain. The core-shell NaYF₄/NaLuF₄: 20%Yb³⁺, 2%Er³⁺ nanocrystals-polymeric methyl methacrylate covalent linking nanocomposites were synthesized and filled into the slot as gain medium. The concentrations of Er³⁺ and Yb³⁺ were increased compared with traditional physical doping methods. High-efficiency emission at 1.53 μm was achieved under 980 nm laser excitation. The slot waveguide was accurately designed using the semivector finite difference method in combination with the maximum confinement factors and the minimum effective mode area. The optimum width of the slot was 200 nm, and the optimum height and width of the silicon strip waveguide were 400 nm and 400 nm, respectively. The six-level spectroscopic model was presented, and the gain characteristics of the slot waveguide amplifier were numerically simulated. A net gain of 8.2 dB was achieved, which provided new ideas and directions for waveguide amplifiers.

Waveguide amplifiers based on slot waveguide have enormous capacity due to their ability to confine light strongly to a narrow slot waveguide. NaYF₄:Er³⁺ nanoparticles-polymeric methyl methacrylate covalently linked nanocomposites were synthesized and filled into the slot. The stability and the Er³⁺ concentration doped in this novel material were improved. The slot waveguide was designed accurately. The rigorous numerical method, full-vector finite difference method, was used to analyze the modal characteristics and optimize the slot combined with the maximum power confinement in the slot and the minimum effective mode area of the slot. A four-level spectroscopic model pumped at 1480 nm was presented. The rate equations and propagation equations were solved and the gain characteristics of the slot waveguide amplifier were numerically simulated. The primary parameters were optimized. A net gain of 5.78 dB was achieved when the signal power was 0.001 mW at 1530 nm, pump power was 20 mW, Er³⁺ concentration was 1.3 × 10²⁷ m⁻³, and the waveguide length was 1.5 cm.

This paper experimentally investigates the perform-ance of free-space optical (FSO) communication based on mode diversity reception (MDR) using nonmode selective photonic lantern (NSPL) and equal gain combining (EGC). By employing a mode demultiplexer and combining technology in the receiver, the bit error rate (BER) and outage performance of FSO communication system can be significantly improved. However, different from diversity system with multiple receive apertures, the branches in mode diversity system are non-independent fading signals, which are influenced by not only atmospheric but also the modal crosstalk of mode demultiplexer. Therefore, we take into consideration the difference of mode demultiplexer and study four schemes for FSO mode diversity reception system: 1) NSPL with equal gain combining (NSPL-EGC), 2) NSPL with maximal ratio combining (NSPL-MRC), 3) mode selective photonic lantern with equal gain combining (MSPL-EGC), and 4) mode selective photonic lantern with equal gain combining (MSPL-MRC). Experimental results show that NSPL-EGC is the most suitable scheme for MDR with low implementation complexity, and the performance difference is less than 1 dB compared with the one using MRC at BER = 3.8×10 ⁻³ under turbulence from weak to strong.

We propose a few-mode erbium-ytterbium codoped polymer optical waveguide amplifier employing mode-selective photonic lanterns capable of multiplexing and demultiplexing. A reconfigurable pump configuration scheme is adopted to balance the modal gain per mode. A square few-mode waveguide amplifier supporting L P 01 , L P 11 a , and L P 11 b modes is designed and fabricated. The crosstalk effect and modal profiles are characterized. An average gain of 10.4 dB per mode is obtained in a 1.5 cm waveguide at 1555 nm through pumping of the L P 01 mode at 320 mW and the L P 21 b mode at 120 mW at 976 nm. The ultralow differential modal gain is 0.4 dB. In addition, simultaneously amplified L P 01 , L P 11 a , and L P 11 b modes are also demonstrated across the whole C-band with low noise figures. To the best of our knowledge, this is the first report of an experimental realization of a few-mode optical waveguide amplifier.